The four types of Shallow Foundation

Shallow foundation is applied in cases where we can find good load-bearing soil at a rather low depth. The foundation depth must meet the safety requirements of the breakdown. That is, after the application of load, the complete structure settlement will be within acceptable limits.

We can use the following four types of shallow foundations: Spread Footing, Combined Footing, Raft Foundation and Ring Foundation.

1. Spread Foundation: You need to spread the load from the column or wall to a larger area, you should use Spread Foundation. The width of the footing area is much wider than the wall or column.

The spread footing that is used to support a wall is called a wall footing or continuous footing. The top of the footing may be stepped or tapered, increasing the width gradually from wall or column to the base. They are of the following types:

a) Strip Footing: This primitive type of footing has been conventionally used in most constructions historically, before more modern inventions. They are mostly made of stones, masonry or concrete. The strip footing that is constructed of stone blocks generally has a stepped top. In modern days, however, the use of strip footing has become next to obsolete. Only in some light loading residential construction is strip footing still used.

b) Isolated Footing: When you provide footings under columns separately in a framed structure, it is called Isolated footing, pad footing or column footing.

In most cases, square footings are used under columns. However, space restrictions may force you to use rectangular footings. In case of circular columns, circular footings may be used, though it is not common. It may be used in special circumstances where construction work is difficult, or the load has to be dispersed very equally.

2. Combined Footing: When two columns are too close to make separate footings for each, then their footings are combined. These may be of the following three types:

a) Rectangular footing: These are the most common types of combined footing. It’s basically two square footings constructed together. This is used when each column is bearing the same load and of the same size.

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Published By
Rajib Dey
www.constructioncost.co
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Construct Earthquake Resistant Buildings by Simple Means

The engineering science is continuing to advance in response to seismic threats. There have been significant breakthroughs in the field. However, most of them are very complex and require exceptional machinery. Not to mention, expensive as well. However, there are some simple ways to build a structure that will be resistant to earthquake damages up to a certain level.

In areas where seismic activity is not too harsh, we can utilize these techniques to same money and complexity but make the building resistant to seismic activities.

Structure Stiffness: The most traditional way to fight quakes is to use stronger materials to construct the building. Stiffer or heavier members can be used to fight the lateral forces generated during seismic activities. For special quake-proof structures, ACI codes prescribe at least 10” thick members.

Geometrical Absorption: The building can be planned in such a regular and special geometrical shape that it disperses the seismic forces evenly so that no particular member experiences excessive force. This naturally fares much better than a poorly-planned unsymmetrical building.

For existing buildings that are structurally asymmetrical, you can use seismic joints and expansion points in places where the forces are dispersed unevenly. Providing extra columns, shear walls, and framing can make the weaker section withstand the extra forces to a good level. Parking levels should have extra reinforced columns in order to negate the soft story effect.

Lateral Force Resistance: Using three types of lateral force resisting systems, we can try to negate much of the seismic forces. These are:

1. Moment Resisting Frame System: it is designed to resist all types of earthquake generated forces acting on the structure. They can be customized to fit the seismic activity scale of the region.

2. Building Frame System: these are designed to resist gravitational loads only, but they function excellently in that. A shear wall is added to resist the lateral forces acting on structure.

3. Dual Frame System: this is a combination of the above two systems. Shear walls along with moment resisting frames work excellently to fight off the vibrations and displacements from an earthquake. But, of course, they are more complex and costlier to build.

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Published By
Rajib Dey
www.constructioncost.co
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Pier foundation and their types, advantages

A pier is kind of a big brother to a column. It is a support structure holding up great loads, and can take a lot of tensile strains as well. Piers are constructed in a dry place by digging out the soil in a large diameter hole and then filling it with reinforcements and concrete. A pile greater than 0.6 meter in diameter becomes a pier.

The pier foundation transfers the load on the pier to the ground via the bearing. It is generally a shallow structure placed on top of sound rock layer. Hard soil is also good for pier foundation construction provided they can take the load.

Types of Pier Foundation

There are two main types of pier foundations, namely:

1. Masonry or concrete pier
2. Drilled caisson

Which type of pier foundation will be used depends upon the depth of the hard bed, nature of soil, and the superimposed load.

Masonry or Concrete Pier Foundation

The name comes from the pier being made of concrete. Precast sections are manufactured in-situ or in facility. Then they are driven into the ground at location. The sections are generally reinforced with steel wires. At the bottom, a cast steel shoe is provided to hold the structure better and to transfer the load well. The cross sections of these piers are generally no more than 30-50 centimeters and they are no taller than 20 meters.

Drilled Caisson Pier Foundation

A drilled caisson is a large compressed member subjected to an axial load. The load is at the top and the reaction is at the bottom. These can be concrete caisson with enlarged bottom, a steel pipe caisson with concrete filled in it, or a concrete body caisson with a steel pipe core.

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Published By
Rajib Dey
www.constructioncost.co
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Basic differences among foundation & footing

Foundation: It is the portion of a building that is built up underneath the ground level and keeps direct contact with sub-strata. It transfers the complete load of the building to the subsoil in which it stands in such a manner that settlement of the soil is not collapsed in shear.

Footing: It is the bottom most part of a vertical structure (column, wall) that finally transmits the weight from walls and columns to the soil or bedrock.

Footing is mainly the segment of foundation of any modern structure.

Variation among footing and foundation

Given below, the basic variations among Footing and Foundation:

1
The footing is a formation that is in touch with the ground.

Foundation belongs to a structure that transfers its gravity loads to earth from superstructure.

2
Footing is analogized with the feet of the leg.
Foundation is compared with legs.

3
The footing refers to a type of shallow foundation.
Foundation is both shallow and deep.

4
Footing comprises of slab, rebar which are made of brickwork, masonry or concrete.
Foundation types comprise piles, caissons, footings, piers, the lateral supports, and anchors.

5
Footing reinforces support to a separate column.
Foundation stands for an extensive support since it provides support to a group of footings as a whole building.

6
A number of footings rest on a foundation.
Foundation is the support that sustains different types of loadings.

7
A footing remains under the foundation wall.
Foundations stand for the basement walls.

8
Footing directly transfers loads to the soil.
Foundation is directly related with the soil and passes it on the ground.

9
All footings are foundations.
Not all foundations are footings.

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Published By

Rajib Dey

www.constructioncost.co

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Some useful construction tips to compute the sliding safety factor for cantilever retaining walls

This construction article is extracted from an exclusive article written by Javier Encinas, the renowned professional engineer Javier Encinas.

The article sheds light on how to compute the sliding safety factor for concrete or masonry cantilever retaining walls.

Retaining walls are specifically created to encircle soils among two dissimilar elevations. So, they have to primarily withstand the lateral pressures from the retained soil as well as any other surcharge. Cantilever walls are susceptible to sliding issues, specifically if constructed on inferior quality soils.

Pressures functioning on a retaining wall
Besides, to the retained backfill, retaining walls are dependent on surcharge loads at the top of retained mass. A surcharge belongs to a strip load. If the stem expands beyond backfill, the retaining wall has to withstand wind load. If the retaining walls are placed in seismic zones, the focus should also be given to seismic pressures.

The load has been used contains a definite effect on the wall. The backfill employs a triangular lateral pressure measured according to the equivalent earth pressure theory. The surcharge creates a constant rectangular pressure on the wall. The seismic pressure is trapezoidal, together with the greater pressure at the top. Due to the actions of these loads, a bearing pressure is created beneath the footing, as well as a passive pressure at the front of the wall.

Method for verifying the sliding failure mode
The wall will be moved to exterior by the horizontal pressures on the backfill side that will have a tendency to slide on its footing. The driving force from the assigned loads should be defied with an opposite friction force at the edge of the footing base and the foundational soil that is formed by the bearing pressure against the base.

Besides, the passive pressure against the front face of the wall and footing should also be taken into consideration. It will never happen that the natural soil will be unaffected throughout the construction, so usually the top portion of the soil cover for the passive force calculation is omitted.

To read the complete article, click on the following link
www.asdipsoft.com

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Published By

Rajib Dey

www.constructioncost.co

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Basic differences between Mortar and Concrete

Concrete and mortar are two most vital building elements for any construction work. But both the materials are different in nature. Go through the following article to know the fundamental discrepancies among concrete and mortar.

Concrete:

Concrete is a composite material produced from a mixture of sand, cement, aggregates and water in required proportions.

Concrete refers to a composite material that is formed with some basic elements like water, aggregate (rock, sand, or gravel) and amalgamated with a fluid cement that hardens in due course.

If aggregate is combined jointly with dry Portland cement and water, it produces a fluid mass that can be smoothly molded into shape. A chemical reaction happens between cement, water and other ingredients to develop a hard matrix that joins the materials together into a strong stone-like material.[2] Sometimes, additives like pozzolans or superplasticizers are provided in the mixture to make the physical properties of the wet mix or the finished material superior.

Mortar:

Mortar is developed by mixing cement, sand and water and applied to tie building blocks like stones, bricks, and concrete masonry units jointly as well as fill and close the uneven gaps among them.

VARIANCE AMONG MORTAR AND CONCRETE:

1. Concrete is developed by mixing cement, sand, aggregates and water, whereas the mortar is formed by mixing cement, sand and water.

2. Concrete is more durable as compared to mortar.

3. The water-cement ratio is greater in mortar. The water is utilized to hydrate the cement and retain the mix collectively. But the objective of concrete is to maintain the water-cement ratio as low as possible.

4. After mixing, Mortar becomes much condensed substance as compared to concrete. Mortar acts like a glue to fix the bricks together. Because of superior strength and longevity concrete is mostly recommended for all types of construction works like buildings, bridges, roads etc.

5. Concrete sustains for a long time but mortar should be substituted by every 20 – 30 years.

Article Source : www.dailycivil.com

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Published By

Rajib Dey

www.constructioncost.co

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Step-by-step guidelines to estimate bricks of a wall

This construction video will introduce you to step-by-step by procedures for estimating the bricks of a wall. The video will provide useful information to select a brick size, lay out modular dimensions with the preferred size as well as generate a materials estimate for brick and mortar.

Brick are formed with different types of sizes and placed in the diverse patterns. Most patterns of brickwork abide by a common module that allows easy dimensioning of the brickwork and any masonry openings.

Usually, it becomes easier for the designers to reduce the number of cuts of entire brick by dimensioning to a module. With a clear idea on the size of the brick and bond pattern, it is possible to produce an estimation of the number of brick and amount of mortar required for the project.

The measurements and dimensions equal to brick manufactured mainly in the United States to a standard module of 4 in. (102 mm). Brick manufactured for projects that needs metric dimensions, generally comply with a module of 100 mm (3.94 in.).

BRICK SIZES

There are different sizes of brick and each size has different utility. As for instance, larger brick are built up to upsurge bricklaying economy, and thinner brick facilitates saving resources.

Brick Orientation

There exist three dimensions for a brick – width alias thickness, height and length. Even though brick is placed in six dissimilar orientations, these dimensions can be applied to a brick that is placed as a stretcher. Height and length are often known as face dimensions, as these dimensions are applicable when the brick is placed as a stretcher.

Brick Dimensions

A brick contains three various sets of dimensions - nominal, specified and actual. Proper care & perfectness should be taken so that any confusion can be evaded throughout design and construction.

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Published By

Rajib Dey

www.constructioncost.co

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Concrete Blocks – Manufacturing Process & Benefits

(1) Raw materials utilized in Concrete Blocks :

The primary materials for developing the concrete blocks are aggregates, cement and water. Different types of aggregates are applied with changeable degree of success and they consist of crushed stones, gravel, volcanic cinders, foamed slag, furnace clinker, etc. In order to choose the aggregates, the factors like weight, texture or composition of the unit designed should be considered. The stability, texture and low-cost of the concrete block are subject to the grading of the aggregate cautiously. The cost will be reduced if locally accessible aggregate is used. The ordinary Portland cement is utilized for raw material. The required water should be the normal potable water.

(2) Concrete blocks manufacturing process:

The completely automatic plants are used to develop concrete blocks with superior strength. These automatic machines can made superior quality concrete blocks. But huge capital investment is required to set up & operate these machines. The transportation cost from the production area to the place of actual use will also be reduced for concrete blocks if the manually operated machines are installed at construction site itself.

The following manufacturing process is required for developing the concrete blocks :-

(i) Choice and ratios of ingredients: The primary factor for selecting the ingredients is the desirable strength of the block. If the coarse aggregate is mixed in perfect ratio, the strength of the quantity of cement applied will be superior.

(ii) Blending of ingredients: The aggregates, cement and water should be blended in a proper way. The mixing should be done through a mechanical mixer. While mixing manually, great care is necessary to check that the cement and aggregates are initially blended comprehensively in dry state and the water is then included slowly.

(iii) Positioning and vibration: The mixed concrete material is delivered into the mould box up to the top level and check carefully that the box is filled uniformly. The vibration of concrete is performed until it is set evenly in the mould box.

(iv) Curing: The block is drenched with water after around one day of casting and it should be sustained for at least 7 days and if possible up to 28 days. If the time for curing extends for a prolonged period, the block will be superior.

(3) Benefits of concrete blocks:The application of concrete blocks as a masonry unit is found on several construction sites due to the following benefits:

• It extends the carpet area of the building due to the small width of concrete block with regards to the brick masonry wall.

• It offers superior thermal insulation, improved fire resistance and strong absorption capacity.

• It can save major agricultural land which is applied for manufacturing bricks.

• The blocks are developed in an efficient manner so that the vertical joints can be taken back automatically and so the time spent for the careful supervision is minimized.

• The process for developing concrete block masonry is simpler, rapid and stronger as compared to the brick masonry.

• The shape and size of the concrete block is very accurate and it simplifies the work of a mason.

• As the numbers of joints are minimized, the time is saved for developing the mortar.

• The utility will be augmented by creating the reinforced concrete block (RCB) masonry units. The blocks are provided with two holes for arranging perfect reinforcing bars and the structure with RCB units could carefully withstand wind and earthquakes, if so designed. The conventional beams and columns are totally removed and the structure with RCB units will have a superior appearance.

Ref: www.theconstructioncivil.org

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Published By

Rajib Dey

www.constructioncost.co

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How to estimate the amount of concrete for pouring a L shaped concrete slab

This construction video briefly explains how to estimate the concrete quantity essential for pouring a L shaped concrete slab in the ground having splayed edge beam and a rebated edge.

Concrete slabs refer to floor systems of concrete and steel reinforcing. These are built on the ground. There are different types of concrete slabs which range from slab on ground, stiffened raft slab, footing slab, waffle raft slab, infill slab.

Edge rebates should be placed in the edge-stiffening beam when exterior walls belong to masonry veneer or complete masonry. A check out from the edge beam will produce a flange for the brick to hinge on under the top of the slab. This extra protection is taken to stop surface run-off water from inflowing the building.

The rebate must be flashed and weep holes are arranged in the masonry. The weep holes should be placed at a least distance of 1.2 metres so that the water can be blown out and left from the wall and the slab.

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Published By

Arka Roy

www.constructioncost.co

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